Continuing with the book idea, I’d like to know what you guys are interested on, regarding our beloved HP15c. More technical details? More programming tips? A systematic listing of all published programs?
A possible avenue would be to port programs from the HP41c. Having access to all solution books, it should be quite easy to achieve a significant number of programs. We must dispense -in my opinion- with all the data entry part and assume that required data is either in the stack or in known registers. Also, we must discard those programs that make reference to extended memory, files, or peripherals, or those that are exceedingly long. Some of my more interesting HP41 programs were of this kind…
Also, I lack the knowledge in many areas about, not only what are the formulas you want to implement for a given problem, but what are the main problems in each discipline! Hence we will have to trust HP’s solution books. My expertise is limited to electrical engineering and finance – so these will probably be well covered.
There is also the fact that computing has progressed enormously since the HP15c was first released in 1982 (which reminds me that this year was its 40th anniversary). By that I mean that the HP41 was all computing many people could afford; and therefore there were programs for it that nowadays you would not dream of executing, waiting instead to sit in front of your excel spreadsheet to solve it. We’ll try to weed out these “non-practical” programs too from our book.
Constants storage is also not too practical when you have just 64 registers. The machine comes with e and pi only – and that should be enough. But in some cases it may make sense. I see this very close to cheating in class.
An interesting area for programs is the one related to education. Many graphical calculators are banned from exams, while the humble HP15c would not be banned, since the exam supervisor would not know how powerful it is. I refer in particular to its programmability and the matrix, solve and integrate features, not seen in most calculators of its size. We can think of program sets for geometry, matrix math, physics, chemistry, statistics and probability, etc. The way this is taught in most schools precludes using the calculator as sole solver of the problem – but it can be used to ensure that your answer is correct. In some cases like small equation systems, it could be used as is – but the bulk of the exam problems will require detailed step-by-step that the calculator cannot provide.
A couple of the initial chapters could be spent explaining the advanced features of the HP15c, and how to integrate them in your programs: matrix, solve, integrate and complex numbers. (in our financial programs, we use the Solve routine to calculate the IRR of an investment based on a short Net Present Value program).
An interesting way of doing it would be to create “program sets”: several programs installed at the same time, with a clever distribution of labels and programs for each application area. It is even conceivable to create overlays for such applications, knowing that it should only cover the letters A to E and the number keyboard (since there is where the program labels should go – the HP15c keyboard was never fully configurable. Only keys A to E under the user mode and numbers 0-9 and .0 to .9, preceded by GSB, could host program label calls.
Again, I am calling for your feedback about what you want to have in such book. You can contact me firstname.lastname@example.org. I promise answering and a healthy discussion!